Linear beam vacuum tube devices dissipate power in the form of waste heat. Requirements for increased power performance and higher frequency operation add thermal dissipation penalities to the tube structure. As the frequency of the linear beam tube increases, the physical size of cavity components decreases. This increases the cavity wall power density. To increase the power handling capability of any cavity configuration, conductive cooling paths must be shortened or the cooling paths must be thermally shorted within the same material volume, thereby reducing the temperature difference between the inside and outside of the cavity wall.